import CmmUtils
import MachOp ( MachRep(..), wordRep, MachOp(..), MachHint(..),
mo_wordOr, mo_wordAnd, mo_wordNe, mo_wordEq,
- mo_wordULt, machRepByteWidth )
+ mo_wordULt, mo_wordUGt, machRepByteWidth )
import ForeignCall ( CCallConv(..) )
import Literal ( Literal(..) )
import CLabel ( CLabel, mkStringLitLabel )
import Outputable
import DATA_BITS
+import Maybe ( isNothing )
#include "../includes/ghcconfig.h"
-- For WORDS_BIGENDIAN
cmmAndWord e1 e2 = CmmMachOp mo_wordAnd [e1, e2]
cmmNeWord e1 e2 = CmmMachOp mo_wordNe [e1, e2]
cmmEqWord e1 e2 = CmmMachOp mo_wordEq [e1, e2]
-cmmULtWord e1 e2 = CmmMachOp mo_wordULt [e1, e2]
+cmmULtWord e1 e2 = CmmMachOp mo_wordULt [e1, e2]
+cmmUGtWord e1 e2 = CmmMachOp mo_wordUGt [e1, e2]
cmmNegate :: CmmExpr -> CmmExpr
cmmNegate (CmmLit (CmmInt n rep)) = CmmLit (CmmInt (-n) rep)
; return (oneCgStmt switch_stmt)
}
+ -- if we can knock off a bunch of default cases with one if, then do so
+ | Just deflt <- mb_deflt, (lowest_branch - lo_tag) >= n_branches
+ = do { (assign_tag, tag_expr') <- assignTemp' tag_expr
+ ; let cond = cmmULtWord tag_expr' (CmmLit (mkIntCLit lowest_branch))
+ ; stmtC (CmmCondBranch cond deflt)
+ ; mk_switch tag_expr' branches mb_deflt lowest_branch hi_tag
+ }
+
+ | Just deflt <- mb_deflt, (hi_tag - highest_branch) >= n_branches
+ = do { (assign_tag, tag_expr') <- assignTemp' tag_expr
+ ; let cond = cmmUGtWord tag_expr' (CmmLit (mkIntCLit highest_branch))
+ ; stmtC (CmmCondBranch cond deflt)
+ ; mk_switch tag_expr' branches mb_deflt lo_tag highest_branch
+ }
+
| otherwise -- Use an if-tree
= do { (assign_tag, tag_expr') <- assignTemp' tag_expr
-- To avoid duplication
}
where
use_switch = ASSERT( n_branches > 1 && n_tags > 1 )
+ {- pprTrace "mk_switch" (ppr tag_expr <+> text "n_tags: "
+ <+> int n_tags <+> text "dense: "
+ <+> int n_branches) $ -}
n_tags > 2 && (small || dense)
-- a 2-branch switch always turns into an if.
small = n_tags <= 4
dense = n_branches > (n_tags `div` 2)
exhaustive = n_tags == n_branches
- n_tags = hi_tag - lo_tag + 1
n_branches = length branches
+ -- ignore default slots at each end of the range if there's
+ -- no default branch defined.
+ lowest_branch = fst (head branches)
+ highest_branch = fst (last branches)
+
+ real_lo_tag
+ | isNothing mb_deflt = lowest_branch
+ | otherwise = lo_tag
+
+ real_hi_tag
+ | isNothing mb_deflt = highest_branch
+ | otherwise = hi_tag
+
+ n_tags = real_hi_tag - real_lo_tag + 1
+
-- INVARIANT: Provided hi_tag > lo_tag (which is true)
-- lo_tag <= mid_tag < hi_tag
-- lo_branches have tags < mid_tag
-- Used for general literals, whose size might not be a word,
-- where there is always a default case, and where we don't know
-- the range of values for certain. For simplicity we always generate a tree.
+--
+-- ToDo: for integers we could do better here, perhaps by generalising
+-- mk_switch and using that. --SDM 15/09/2004
emitLitSwitch scrut [] deflt
= emitCgStmts deflt
emitLitSwitch scrut branches deflt_blk